We have been using the KANBAN board, and we've had a very long sprint (going on two months). I wanted to move the CLOSED issues into a different sprint so I could negotiate the board more easily. I set up a new sprint, selected the issues in BACKLOG view and dragged them into the new sprint. Now, they have all disappeared. They are not in the current sprint or in the new one I created. Issue searching for CLOSED issues isn't finding them either. How can I recover these?